Ultraviolet (UV) albedo and UV reflectance are defined, compared and contrasted, to explain their roles and place in studies focusing on UV radiation and exposure measurements, in the context of localised albedo measurement and human UV exposure studies. This review recommends that the term UV albedo be used when investigating natural horizontal surfaces when the albedo is not known to change significantly over time. The term UV reflectance should be mostly used for non-natural surfaces and non-horizontal measurements and will change with respect to the geometry of the irradiances reflected and received, and due to the intrinsic nature of the surface itself. UV albedo measurements made in the literature have been compiled, in both broadband and spectral UV albedo measurements. Broadband measurements have been tabulated and spectral UV measurements have been displayed visually. The methodology of measurements is briefly discussed. Finally, studies that consider how high albedo or reflectance sites influence UV exposure are reviewed. It was concluded that there is currently no known relationship between the albedo or reflectance of a surface and the resulting influence it has on individual UV exposure. This presents an opportunity for researchers to continue exploring the influence of reflective UV surfaces.
31 October 2008 in Photochemical & Photobiological Sciences
Erythemal UV exposure for individuals involved in outside activities are affected according to surrounding structures in an urban environment. Occupational UV exposure is likely to increase by the effects of surrounding structures. UV reflections from surrounding structures, in this case vertical metal walls, were investigated for their influence on erythemal UV exposure in the southern hemisphere. Multiple dosimeters were placed at specific features on head forms, for three different vertical wall conditions, measured at hourly intervals, providing a more detailed representation of the effect of nearby (north facing) reflective wall, non-reflective wall and no wall on UV exposure for a construction worker facing the wall direction. Two types of metal sheeting walls were investigated, with the first type (shiny and smooth in appearance) showing results that indicate the UV reflectance from this surface can increase the average erythemal UV exposure by at least 20% and up to an average of 50% for certain facial positions, compared to no wall and up to 300% compared to a non-reflective wall. A second metal sheeting type coated with colour, does not show as much influence on UV exposure for larger solar zenith angles compared to the first type of metal sheeting, but for smaller solar zenith angles provides an influence that approaches similar erythemal UV exposure to that when no wall is present. The time to reach the exposure limits defined by regulatory bodies for occupational UV exposure can be decreased if the first type of metal sheeting is in proximity to an outdoor worker. The experimental method of this study leads to discussion of how metal surfaces used in the construction industry physically reflect UV radiation. The conclusion is that albedo, which is traditionally used to measure UV reflection, is not an appropriate quantity to explore UV reflection from vertical metal surfaces. This may be due to the reason that metal surfaces seem to involve specular reflection as well as diffuse reflection.
Excessive exposure to solar ultraviolet (UV) radiation has damaging effects on life on Earth. High-energy short-wavelength ultraviolet B (UVB) is biologically effective, influencing a range of dermal processes, including the potentially beneficial production of vitamin D. In addition to the damaging effects of UVB, the longer wavelength and more abundant ultraviolet A (UVA) has been shown to be linked to an increased risk of skin cancer. To evaluate this risk requires the monitoring of the solar UVA globally on a time repetitive basis in order to provide an understanding of the environmental solar UVA irradiance and resulting exposures that humans may receive during their normal daily activities. Satellite-based platforms, with the appropriate validation against ground-based instrumentation, can provide global monitoring of the solar UVA environment. Two satellite platforms that currently provide data on the terrestrial UVA environment are the ozone monitoring instrument (OMI) and the global ozone monitoring experiment (GOME-2). The objectives of this review are to provide a summary of the OMI and GOME-2 satellite-based platforms for monitoring the terrestrial UVA environment and to compare the remotely sensed UVA data from these platforms to that from ground-based instrumentation.